1. Field of the Invention
This invention pertains to step opening valves and in particular to servo regulated, step opening gas valves.
2. Description of the Prior Art
In the prior art, combination gas valves having a main diaphragm operated valve and a servo regulator which regulates the output pressure by controlling the pressure in a control chamber relative to the inlet pressure are well known. For example, see U.S. Pat. Nos. 3,447,755 and 3,592,225. Also in the prior art, it is well known to provide for a two stage valve in which a diaphragm opens a first valve and a lost motion connection between the diaphragm and a second valve allows the second valve to be opened when the diaphragm moves further toward the open position. See U.S. Pat. No. 3,279,498, Finally, U.S. Pat. No. 2,262,825 is pertinent for the teaching of a diaphragm shut-off valve and a plurality of poppet plates which seat on an auxiliary valve surface downstream therefrom.